Coaxial cables in which a core conductor is covered by a dielectric, the outer circumference of this dielectric is covered by a shielding layer composed of a conductor, and the outer circumference of this shielding layer is covered by an outer covering (jacket), are generally known, and are widely used as high-frequency transmission lines. In recent years, such coaxial cables have become increasingly fine; for example, extremely fine coaxial cables in which the diameter of the core conductor is 0.1 mm or less, and the external diameter of the coaxial cable is approximately 0.35 mm, have begun to be used in electronic devices such as compact notebook type personal computers, portable telephones and the like.
In such electronic devices, for example, a plurality of coaxial cables are used to establish electrical connections between the liquid crystal display part and main body part of a notebook type personal computer via a hinge with a small diameter, and such wiring and connections become complicated. Flat cables which are constructed by holding a plurality of coaxial cables parallel to each other in the same plane have been used as a means of establishing such complicated connections easily and securely. For instance, one example of such a flat cable is described in JP Patent Application No. 2004-27333. However, in the flat cable of this application, accurate maintenance of the pitch interval that is formed between the coaxial cables of the flat cable when the terminal treatment of the cable is performed after the flat cable is passed through a small-diameter hinge is difficult, and the terminal treatment is problematical.
Furthermore, there are cases in which braided cables that are braided using a plurality of coaxial cables are used, for example, in the electrical connections between the liquid crystal display part and main body part in portable telephones and the like. Here, however, as was described above, accurate maintenance of the pitch interval that is formed between the cables when the terminal treatment of the cable is performed after the cable is passed through a small-diameter hinge is difficult, and the terminal treatment is problematical.
In portable telephones (hereafter referred to as “terminal devices”), progress has been made in reduction of the size and weight of such terminal devices, and in the increased functionality of such devices, and there is therefore a demand for complicated wiring and connections in spite of the limited space inside such terminal devices. Furthermore, in regard to the configuration of such terminal devices, in addition to the so-called folding type configuration in which a movable part on which a liquid crystal display part is formed opens and closes by pivoting about the main body part, terminal devices with a new configuration in which the movable part is attached to the main body part so that this movable part can rotate in addition to folding have appeared on the scene in recent years.
In the abovementioned folding type and rotary type terminal devices, the movable part and main body part are connected via a cylindrical hinge that has a small diameter, and the liquid crystal display part and main body part are electrically connected by passing the abovementioned flat cable or braided cable through the hinge hole of the abovementioned hinge. Thus, flat cables or braided cables have come to be used in terminal devices; however, in the case of the flat cable or braided cable described in JP Patent Application No. 2004-27333, the cable is subjected to cable terminal working that accurately maintains the pitch interval between the coaxial cables in the flat cable or braided cable at a fixed value before the cable is passed through the hinge, e.g., a terminal treatment in which the respective coaxial cables are connected to the terminals of a connector or to an FPC (flexible printed circuit). If this is not done, accurate maintenance of the pitch interval after the cable has been passed through the hinge becomes difficult when the liquid crystal display part and main body part are electrically connected via the abovementioned cylindrical hinge that has a small diameter. On the other hand, if a terminal treatment is performed before the cable is passed through the hinge in order to ensure accurate maintenance of the pitch interval, the diameter of the terminal treatment part is increased, so that it becomes impossible to pass the cable through the hinge. However, it may be predicted that there will be a further diversification of terminal device configurations into various configurations in the future. On the one hand, taking into account the fact that there will be further progress in the reduction in size and weight of terminal devices, and the increased functionality of such terminal devices, the appearance of flat cables that allow the easy and secure accomplishment of complicated and difficult electrical connections, and flat cables that can ensure a uniform pitch between the coaxial cables, is to be hoped for.
The present invention was devised in light of the various problems described above; it is an object of the present invention to provide a flat cable which is superior in terms of softness and flexibility, which can be passed through an extremely narrow through-hole, which can favorably maintain the precision of the pitch between the coaxial cables, and which allows the easy and secure accomplishment of complicated and difficult electrical connections.